How can an equidistance, spherical panorama image be generated from Blender Cycles?
This is natively supported in Cycles.


Set your output resolution at a 2x1 ratio (e.g. 2048x1024).
Select the camera.
In the properties window, camera tab, select "Panoramic."
For "Type" select Equirectangular.


Here's what it looks like for me: